What 11 Billion People Mean for Climate Change

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Editor's note:By the end of
this century, Earth may be home to 11 billion people, the United
Nations has estimated, earlier than previously expected. As part
of a week-long series, LiveScience is exploring what reaching
this population milestone might mean for our planet, from our
ability to feed that many people to our impact on the other
species that call Earth home to our efforts to land on other
planets.Check
back hereeach day for the next installment.

On the western coast of Alaska, nestled against the Bering Sea,
residents of the remote village of Newtok may soon become the
country's first climate refugees.

Like many Alaskan villages, Newtok sits atop permanently frozen
soil called permafrost. In recent years, however, warming oceans
and milder surface temperatures have melted the icy subsoil,
causing the ground beneath Newtok to erode and sink. In 2007, the
village already sat below sea level, and studies warned that the
subarctic outpost could be completely washed away within a
decade.

Now, despite political and financial hurdles, the community is
looking to relocate its roughly 350 residents. With climate
change rapidly altering human ecosystems around the globe, Newtok
may not be alone in its fight against warming temperatures,
melting ice and rising seas.

For the roughly 7.2 billion people who live on Earth today, the
impacts of a changing climate
may be taking different forms, but the consequences are already
being felt across the globe — from severe monsoons in Southeast
Asia, to the increasing pace of melting ice at the poles, to
hotter-than-average temperatures throughout the contiguous United
States.

Over the course of the next century, if the levels of greenhouse
gas emissions are not reduced, and nations have failed to
address the myriad challenges of climate change, scientists say
Earth's fragile ecosystem could be in serious jeopardy. But, what
if in those same 100 years, nearly 4 billion people are added to
the world's population? Could this type of rapid growth overwhelm
the carrying capacity of our "Pale Blue Dot" and our ability to
mitigate and cope with climate change?

A recent United Nations analysis of world
population trends indicates global population growth shows no
signs of slowing, with current projections estimating a
staggering 11 billion people could inhabit the planet by the year
2100, faster growth than previously anticipated. The majority of
this surge in population is likely to occur in sub-Saharan
Africa, with the population of Nigeria expected to surpass that
of theUnited States before 2050, according to the statistical
analysis.

The new report also suggests India will eventually become the
world's largest country, matching China's estimated
population of 1.45 billion people in 2028, and continuing to
swell beyond that point, even as China's population begins to
decrease.

Some scientists say rapid population growth could be catastrophic
for the planet, because it will likely lead to overcrowding in
cities, add stress to Earth's already dwindling resources, and
worsen the effects of climate change. But within the scientific
community, a debate is brewing, and there is little consensus
about how — or even if — population growth is linked to global
warming.

Assessing the impact of population growth on climate change has
been tricky. Most scientists agree that humans are to blame for
most of the planet's warmingsince 1950, but precisely which
events were aggravated by human activities (and how much) are
unknown. [ What
11 Billion People Mean for the Planet ]

"It's a question that's really hard to answer, because climate
science is not to the point of being able to identify specific
impacts, or changes that have occurred so far, as being directly
caused by climate change," said Amy Snover, co-director of the
Climate Impacts Group and a researcher at the Center for Science
in the Earth System at the University of Washington in Seattle.
"What we can do is look at the many things that have happened
recently that are similar, and what we expect to happen, and see
that these things are problematic and will certainly raise
concerns for the future."

Furthermore, scientists on both sides of the equation — those who
study demographics and those who study climate science — do not
necessarily agree on how, or even if, population growth and
climate change are connected.

A growing debate

Increasing the number of people on the planet does not, in
itself, intensify climate change, said David Satterthwaite, a
senior fellow studying climate change adaptation and human
settlements at the International Institute for Environment and
Development, in the United Kingdom. Rather, changes in
consumption are the key drivers of global warming, he explained.

"Higher consumption is what drives anthropogenic climate change,"
Satterthwaite told LiveScience. "The high-consumption lifestyles
of the richest half-billion people scare me much more than the
growth in population in low-income nations."

This is because developing nations, where the U.N. estimates most
of the next century's surge in population will occur, have much
smaller carbon footprints than developed countries, such as the
United States, Canada and the United Kingdom.

"If you think of population as the driving force, it makes sense
to look at the fast-growing nations and say: 'We have to slow
that population growth,'" Satterthwaite said. "But most of the
nations with the fastest growing populations have far lower
per capita greenhouse gas emissions."

During the Industrial Revolution, which began in the mid-1700s in
England and later spread across the Atlantic Ocean to the United
States, emissions of carbon dioxide and other heat-trapping gases
soared as manufacturing and transportation boomed. The
technologies used during the Industrial Revolution were also
inefficient and largely based on coal and fossil fuels, which
emit large amounts of greenhouse gases that linger in the
atmosphere.

This flurry of activity has taken a toll on the planet. Since the
start of the Industrial Revolution, human activities have
increased the concentration of atmospheric carbon
dioxide by a third, according to NASA.

Now, as developing countries seek their own industrial
revolution, there are concerns that too much damage has already
been done.

"There are opinions that we're already past a sustainable
population now, in terms of being able to provide a high quality
of life for every citizen on the planet," said David Griggs, a
climatologist and director of the Monash Sustainability Institute
at Monash University in Melbourne, Australia, and a former head
of the
Intergovernmental Panel on Climate Change (IPCC), an
international body jointly established by the United Nations
Environment Programme and the World Meteorological Organization
to assess the environmental and socioeconomic impacts of climate
change.

Others say improvements in technology will yield better crop
production and distribution, enabling cities and towns to
accommodate more people, he added. But more is not necessarily
better.

"I'm not a fan of thinking about this as a tipping point — there
isn't a point where we just go over the edge," said Griggs, who
was previously the deputy chief scientist of the United Kingdom's
national weather service. "It's a slow deterioration, and the
more people there are, the more challenging it is for those
people to have their basic needs met."

Population versus consumption

To understand the potential environmental impacts, it is
important to consider both population growth and trends in
consumption, said Robert Engelman, president of the Worldwatch
Institute, an environment and sustainability think tank based in
Washington, D.C.

"Some people will say one matters more than the other, but they
multiply each other," Engelman said. "It would be dangerous to
ignore population as a major factor."

In 2008, China, the United States, the European Union (excluding
Estonia, Latvia and Lithuania), India, the Russian Federation,
Japan and Canada were among the top emitters of carbon dioxide.
Combined, these nations contributed more than 70 percent of the
global carbon dioxide emissions from fossil fuel combustion
and industrial processes. In contrast, the rest of the world
represented only 28 percent of carbon dioxide emissions.

"In some of the poorest countries in the world, emissions are
very low, but the idea is we want these countries to develop,"
Engelman said. "As we've seen happen in India and China as
they've industrialized, countries that are populous and poor can
experience a rapid rise in greenhouse gas emissions. We can't
just consider how much the average person is emitting in these
populous countries now. We have to think about what will be
happening to the people in these countries over the next 70
years."

Beginning in the 1960s, China embarked on a rapid path toward
industrialization. By the end of the century, the country had
secured its place as a manufacturing powerhouse and a veritable
economic superpower. But, China's speedy industrialization has
come at an environmental cost.

Within 20 years, China more than tripled its emissions of carbon
dioxide — from 2.46 million tons of carbon dioxide in 1990 to
8.29 million tons in 2010, according to United Nations estimates.

Since 2000, China's energy-related greenhouse gas emissions have
increased at an average rate of more than 10 percent each year,
according to the Harvard Project on International Climate
Agreements, which is designed to identify "scientifically sound,
economically rational, and politically pragmatic post-2012
international policy architecture for global climate change."

But, developing climate policies has been a challenging, and an
often fruitless, process.

Jerry Karnas, the Center for Biological Diversity's population
campaign director in Miami, is all too familiar with these
political pitfalls, particularly in addressing the impact of
population growth on climate change.

In 2008, Karnas was appointed to a statewide commission to help
design a plan for Florida to reduce its carbon dioxide emissions
to 80 percent of 1990 levels by the year 2050. The final report
was more than 1,000 pages and comprehensively tackled every
sector of Florida's economy, except population.

"Population was the only thing not on the table," Karnas said.
"We had to take growth as a given, and not challenge the notion
that for Florida to succeed, it had to grow."

One of the reasons the state government accepts rapid population
growth has to do with the way Florida's economy is set up, Karnas
said.

"Florida is a sales tax state. We have no income tax, but much of
the state is also funded by the documentary stamp tax," he said.
"Documentary stamps are real estate transactions, so every time a
real estate transaction occurs, it gets taxed, and that goes into
the state coffer. So, the two major funding sources for Florida
are dependent on increasing the population numbers in the state."

While the
population of the United States is not expected to leap
significantly in the next century, diminishing natural resources
are already adding stress to the country's food and water
supplies, and the availability of future energy resources.

If the global population increases by 3 billion people, food
production will also need to rise to meet these growing
demands. Finding adequate agricultural land, however, will be a
challenge, as soil erosion and more frequent droughts related to
climate change render larger tracts of land unusable, Griggs, the
Monash University climatologist, said.

"If we look at the next 50 years, we'd need to grow more food
than we have in the whole of human history to date to feed those
9 billion people," Griggs said. "But since we have no more
agricultural land, we'll have to produce all this food on the
same land we're producing food on at the moment."

In particular, southern Asia, western Asia and northern Africa
have virtually no spare land available to expand agricultural
practices, according to the 2013 Statistical Yearbook of the Food
and Agricultural Organization for the United Nations, published
in June.

In the United States, the Bureau of Reclamation released a report
on the status of the Colorado River Basin in December 2012. The
study concluded that over the next 50 years, water supply from
the Colorado River will be insufficient to meet the demands of
its adjacent states, including Arizona, New Mexico and
California.

"The U.S. government was effectively saying, there will be no way
to completely satisfy the water needs of the population that is
currently projected in that part of the country," Engelman said.

Worldwide, the situation is not much better. A 2011 report on the
state of the world's land and water resources, released by the
Food and Agriculture Organization of the United Nations,
established that more than 40 percent of the world's rural
population lives in water-scarce regions.

Ways to mitigate the impacts

While the impact of population growth on climate change remains a
topic of debate, experts agree that finding ways to mitigate the
effects of climate change will be critical for the sustainability
of the planet.

For one, nations need to address climate change issues now, in
order to make communities more resilient in the future, said
Declan Conway, a professor of water resources and climate change
at the University of East Anglia in the United Kingdom. This
includes investing in renewable
energy alternatives, such as technologies to efficiently
harness solar and wind energy, he added.

As part of his work at the Worldwatch Institute, Engelman also
promotes the idea of
carbon taxes, which would introduce fees based on the carbon
content of fuels. While these types of resource taxes have been
suggested as an incentivized way to reduce greenhouse gas
emissions, they remain politically divisive.

Still, others see positive changes on the horizon.

"Twenty years ago, climate change wasn't seen as an issue at all,
but since then, technology has improved rapidly," Griggs said.
"We don't have to hang around and wait for something bad to
happen. There's no question that we can deal with all of these
climate change issues now, if we want to. The real issue is: Will
we? Will there be the political will and the leadership to take
on these things?"

As for whether he remains optimistic overall, Griggs is a little
more hesitant. "I'm schizophrenic about it," he said. "[At]
times, I look at what's happening in the world and the lack of
progress, and I say, we're stuffed. On my good days, I'm
optimistic and I see us moving in a direction that will allow us
to solve these problems."